Electric switches of large power comprising axially movable switching rods and resilient annular fixed contacts which are in permanent contact with said switching rods and contact strips for such fixed contacts

ABSTRACT

An electric switch having an axially movable switching rod and a fixed contact which is in permanent contact with said switching contact. The fixed contact comprising a zigzag folded metal contact strip which is bent in the shape of an uninterrupted ring. The inner circumference of said ring is bent in the shape of longitudinally split tubes extending in the direction of the width of said strip and interconnecting the parts of the folded strip that adjoin each other at said inner circumference.

United States Patent [7 21 Inventors Rintje Boersma Harmelen; GijsbertW. Irik, Bilthoven, Netherlands 21] Appl. No. 867,796 [22] Filed Oct.20, 1969 [45] Patented Mar. 2, 1971 [73] Assignee N.V. COQ

Utrecht Kanaalweg, Netherlands [32] Priority Apr. 15, 1969 [33Netherlands 3 l 1 69.05749 [54] ELECTRIC SWITCHES OF LARGE POWERCOMPRISING AXIALLY MOVABLE SWITCHING RODS AND RESILIENT ANNULAR FIXEDCONTACTS WHICH ARE IN PERMANENT CONTACT WITH SAID SWITCHING RODS ANDCONTACT STRIPS FOR SUCH FIXED CONTACTS 6 Claims, 5 Drawing Figs.

[52] US. Cl

[51] Int. Cl .6 Htllh l/10 [50] Field of Search 200/166 (B1), 166 (B8)[56] References Cited UNITED STATES PATENTS 2,975,254 3/1961 Yanagisawa...200/l66(B1)(X) 3,087,038 4/1963 Bethke 200/166(Bl) PrimaryExaminer-4i. 0. Jones Attorney-Snyder and Butrum ABSTRACT: An electricswitch having an axially movable switching rod and a fixed contact whichis in permanent contact with said switching contact. The fixed contactcomprising a zigzag folded metal contact strip which is bent in theshape of an uninterrupted ring. The inner circumference of said ring isbent in the shape of longitudinally split tubes extending in thedirection of the width of said strip and interconnecting the parts ofthe folded strip that adjoin each other at said inner circumference.

3; 567,892 PATENTEB "AR 2 I97! INVENTORQ RiNra'E 805R A eia'sssnr w. K

BY9 Www ATTORNEYS The invention relates to an electric switch of largepower comprising an axially movable switching rod and a resilientannular fixed contact which is in permanent contact with said switchingrod and is adapted to connect said switching rod electricallyconductively with the circuit to be closed and opened by said switch,said fixed contacts consisting of a zigzag folded metal contact stripwhich is surrounded and supported by an annular holder and is bent inthe shape of an uninterrupted ring, which snugly encloses the switchingcontact.

Annular fixed contacts of this kind are known in many shapes. If thefolded contact strip of such a fixed contact is arranged, as is usual,with the bisectors of the angles, enclosed between its adjacent partsdiverging in V-shape, in radial direction to the switching rod, theresilience of the strip is very tough and there is the risk that thecontact strip does not lie with all folds at the inner circumference ofthe ring formed by said strip against the switching rod withsubstantially equal pressure and that some of said folds do not touchthe switching rod at all. More over, the number of contact placesbetween the contact strip and the switching rod and between said rod andthe holder of said strip is restricted, which may lead at largecurrents, e.g. short circuit currents, to the burning-out of said strip.If the contact strip is directed with its parts in more tangentialdirections to the switching rod the resilience is more elastic and thenumber of contact places between the strip and the switching rod andbetween said strip and the holder can be increased, but then the coolingof the strip in the contact places appears to be worse, which may alsolead to burning-out at short circuit. The parts of the strip must thenstill join each other at the inner circumference of the contact ringsomewhat in V-shape, so that the possible number of contact places isdecreased again. In the fixed contacts of the described kind the bestarrangement is always a comprise between the resilience, the number ofcontact places and the cooling.

The invention has for its object to provide a switch comprising aswitching rod and a fixed contact consisting of a folded contact stripand being in permanent contact with said rod, in which the parts of thecontact strip lie against the switching rod with well reproducibleresilience,'the number of contact places can be large and s satisfactorycooling of said contact places is obtained. The invention consists inthat the said contact strip is folded in such a manner, that the partsof each individual pair of adjacent parts thereof are interconnected atthe inner circumference of said ring by a portion of the contact stripwhich is bent in the shape of a split tube extending in the direction ofthe width of said strip. Consequently, the strip is bent tubularly inthe contact places. Owing thereto not only the resisting moment of thecontact strip is increased in the contact places but also a satisfactorycooling in said places becomes possible. Due to this better cooling itbecomes possible to lay two parts of the strip interconnected by such atubular portion very close or even completely one against the other,which means that, considering that the parts of the strip have to extendtangentially to the switching rod, a reproducible well-elasticresilience of said parts is obtained and the number of contact places anbe relatively large. Load tests have proved that the fixed contactmanufactured in accordance with the invention is resistant toconsiderably larger currents than the fixed contact, of which the foldedstrip does not have the tubular portions in the contact places.

Advantageously, the fixed contact of the switch may be constructed insuch a manner, that one part of each pair of adjacent partsinterconnected by a tubular portion of the contact strip merges smoothlyand the 7 other part thereof merges through a fold extending in thedirection of the width of said strip into said tubular portion. In thisconstruction the parts of the strip come to lie near the contact places,a bit farther from the switching rod, whereby the cooling is stillfurther improved.

Preferably, each tubular portion interconnecting two adjacent parts ofthe contact strip and at least the end portions of said parts adjoiningsaid tubular portion are curved both in the direction of the width ofsaid strip and in a plane at right angles with the plane of said strip.This prevents that the switching rod is scraped by edges of the strip,when said rod is moved through the fixed contact. Thereby the movementof the switching rod through the fixed contact is facilitated andthe'risk that the switching rod takes the strip along during itsmovement, whereby the latter is deformed in cross direction, is reducedpractically to mil.

The invention also relates to a contact strip for the mentioned fixedcontact of the described switch, said co'ntact strip being constructedin such a manner, that the parts of each individual pair of adjacentparts of the contact strip are interconnected by a portion of said stripwhich is bent in the shape of a split tube extending in the direction ofthe width of said strip. If necessary, each tubular portioninterconnecting two adjacent parts of the contact strip and at least theend portions of said parts adjoining said tubular portion may be curvedboth in the direction of the width and in a plane at right angles withthe plane of said strip.

The invention will be elucidated with the aid of the drawing. Thereinis:

FIG. 1 partly an axial sectional view, partly an elevational view of aswitching rod and a fixed contact which is permanently in contact withsaid rod of a switch of large power according to the invention;

FIG. 2 a cross sectional view taken on the line Il-Il in FIG.

FIG. 3 in perspective a portion of a contact strip for the mentionedfixed contact of such a switch;

FIG. 4 in perspective a portion of a variant of the contact strip shownin FIG. 3 and used in the fixed contact shown in FIGS. 1 and 2; and

FIG. 5 in perspective a portion of a variant of the contact strip shownin FIG. 4.

ln FIGS. 1 and 2 an axially movable switching rod of an electric switchof large power is designated by 1. Provided for the permanent connectionof the switching rod 1 with the outer circuit is a fixed contact whichconsists of an annular metal holder 2 and a contact strip 3 supported bysaid holder. The contact strip 3 consists of a zigzag folded metal stripwhich is bent in the shape of a ring snugly enclosing the switchingrod 1. The parts 3, 3" of the folded strip 3 extends closely and almostparallel to each other in pairs and they are directed nealy tangentiallyto the switching rod 1 (see FIG. 2).

The two parts 3', 3 of each pair of substantially parallel parts areinterconnected at the inner circumference of the ring formed by thestrip 3 by a portion 4 of the strip which is bent in the shape of asplit tube. The strip 3 is resiliently forced against the switching rod1 with the tubular portions 4. The tubular shape of the strip 3 in thecontact places between the fixed contact 2, 3 and the switching rod 1improves the cooling in said places.

In the embodiment shown in FIG. 3 the tubular portion 4 of the strip 3is symmetrically positioned in respect of the parts 33" interconnectedby said portion 4. In FIGS. 2 and 4 the tubular portion 4' isasymmetrically positioned in such a manner, that the part 3' mergessmoothly and the part 3" merges through a fold 5 extending in thedirection of the width of said strip into said tubular portion 4'. Dueto this construction a somewhat better cooling of the contact places isobtained.

In the variant shown in FIG. 5 the tubular portion 4" and the endportion of the parts 3', 3" of the contact strip adjoining said portion4" are somewhat curved in the direction of the width and transversely tothe plane of the strip. Owing thereto the edges of the strip come to lieagainst the switching rod 1 with little or no pressure, so that it isavoided, that during the movement of the switching rod said edges of thestrip scrape over the surface of said rod, whereby the switching rodcould be damaged and the contact strip could be taken along with theswitching rod through a small distance.

We claim:

1. An electric switch of large power comprising an axially movableswitching rod, a resilient annular fixed contact which is in permanentcontact with said switching rod to connect same with the circuit to beclosed and opened by the switch, an annular holder and a zigzag foldedmetal contact strip which is surrounded and supported by said holder andbent in the shape of an uninterrupted ring that snugly encloses saidswitching rod, said holder and said contact strip constituting togethersaid fixed contact, the parts of each individual pair of adjacent partsof sad contact strip interconnected at the inner circumference of saidring by a portion of said contact strip which is bent in the shape of alongitudinally split tube extending in the direction of the width ofsaid contact strip.

2. An electric switch as claimed in claim 1, in which one part of eachpair of adjacent parts interconnected by a tubular portion of saidcontact strip merges smoothly and the other part thereof merges througha fold extending in the direction of the width of said contact stripinto said tubular portion.

3. An electric switch as claimed in claim 1, in which the parts of eachpair of adjacent parts interconnected by a tubular portion of thecontact strip lie practically against each other.

4. An electric switch as claimed in claim 1, in which each tubularportion interconnecting two adjacent parts of said contact strip and atleast the end portions of said parts adjoining said tubular portion arecurved both in the direction of the width of and at right angles withsaid parts.

5. A zigzag folded metal contact strip for a fixed contact of theelectric switch claimed in claim 1, in which the parts of eachindividual pair of adjacent parts of said contact strip areinterconnected by a portion of said strip which is bent in the shape ofa longitudinally split tube extending in the direction of the width ofthe contact strip.

6. A zigzag folded metal contact strip as claimed in claim 5, in whicheach tubular portion interconnecting two adjacent parts adjoining saidtubular portion are curved both in the direction of the width and atright angles with said parts.

1. An electric switch of large power comprising an axially movableswitching rod, a resilient annular fixed contact which is in permanentcontact with said switching rod to connect same with the circuit to beclosed and opened by the switch, an annular holder and a zigzag foldedmetal contact strip which is surrounded and supported by said holder andbent in the shape of an uninterrupted ring that snugly encloses saidswitching rod, said holder and said contact strip constituting togethersaid fixed contact, the parts of each individual pair of adjacent partsof sad contact strip interconnected at the inner circumference of saidring by a portion of said contact strip which is bent in the shape of alongitudinally split tube extending in the direction of the width ofsaid contact strip.
 2. An electric switch as claimed in claim 1, inwhich one part of each pair of adjacent parts interconnected by atubular portion of said contact strip merges smoothly and the other partthereof merges through a fold extending in the direction of the width ofsaid contact strip into said tubular portion.
 3. An electric switch asclaimed in claim 1, in which the parts of each pair of adjacent partsinterconnected by a tubular portion of the contact strip lie practicallyagainst each other.
 4. An electric switch as claimed in claim 1, inwhich each tubular portion interconnecting two adjacent parts of saidcontact strip and at least the end portions of said parts adjoining saidtubular portion are curved both in the direction of the width of and atright angles with said parts.
 5. A zigzag folded metal contact strip fora fixed contact of the electric switch claimed in claim 1, in which theparts of each individual pair of adjacent parts of said contact stripare interconnected by a portion of said strip which is bent in the shapeof a longitudinally split tube extending in the direction of the widthof the contact strip.
 6. A zigzag folded metal contact strip as claimedin claim 5, in which each tubular portion interconnecting two adjacentparts adjoining said tubular portion are curved both in the direction ofthe width and at right angles with said parts.